To ensure the safety of the passengers and crewmembers in case of a depressurization accident or the occurrence of smoke in the aircraft, aviation regulations require on board all airliners a safety oxygen supply circuit able to supply each passenger and crewmember with an oxygen flow rate function of the cabin altitude. Such oxygen is delivered to the crewmember or passenger, also known as end user, through a breathing mask.
After a depressurization accident or upon the occurrence of smoke in the aircraft, the users must don their protective mask upon their face as quickly as possible. Indeed, the lack of oxygen at high altitude (hypoxia) or the toxic fumes can alter the users' abilities to proceed with any emergency measures.
For crewmember, the breathing mask comprises an on-demand regulator which is able to regulate the gas inside the breathing mask in term of oxygen content and pressure. This type of regulator is well known in the art and is disclosed, for instance, in document U.S. Pat. No. 6,789,539 which is incorporated herein by reference.
The protective mask is generally stored in a box called a stowage box located next to the crewmember's position. Generally, the stowage box comprises a frame forming a receptacle for the mask, itself having an open face of rectangular shape for inserting and extracting the mask, and at least one door closing the open face of the frame, at least in part. The box is installed on the right or left of the seat of the pilot, the open face being generally the top side of the box. The stowage box comprises a pneumatic assembly able to close the feed of breathing gas of the breathing mask when the breathing mask is installed in the stowage box. The objective of the pneumatic assembly is to reduce or suppress the consumption of breathing gas when the mask is not in use. Therefore, the pneumatic assembly is connected to one of the doors of the box such that the feed of breathing gas is closed when the doors are closed and is open when the doors are open.
For instance, patent application US 2004/0144384, which is incorporated herein by reference, discloses such a box.
The box is generally disposed around the seat of the crewmember. However, a problem with such a box is that it occupied a space which is precious as a lot of equipments need to be arranged around the crewmember.
For passenger, the breathing mask is much simpler and comprises generally a simple plastic cup with straps. The plastic cup is connected through a plastic hose to an oxygen source. The breathing mask is stowed in a box disposed in the ceiling, above the passenger. In case of emergency, a crewmember, through some automatic means, opens the box and the plastic cup falls in front of the passenger's face, just maintained by the plastic hose, but which is enough due to the weightlessness of the cup. The passenger takes the cup, put it on its face and adjusts the straps around his/her head to maintain it.
However, this type of breathing mask is not satisfactory in place where the stowage box cannot be installed in the ceiling above the user. For instance, in some aircraft toilet, the stowage box position is far away from the user. Thus, the supply hose length is such that the mask falls down on the floor which is neither practical nor hygienic.
Furthermore, when passengers are professionals, who work in the aircraft like postmen in a cargo aircraft, or very important persons travelling in a private aircraft, there is a demand to install on-demand breathing masks for these passengers. However, due to the weight of such a mask, often many hundred grams or so, it is not possible to let it fall from a ceiling box as the plastic cup and therefore, installation of on-demand breathing masks for passengers is limited nowadays to the capability to change the cabin layout to install the same boxes than those used for crewmembers.